patch for sscanf issues

patch for sscanf issues

[gs]

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the current sscanf implementation has 2 issues:
- it doesnt return EOF with fscanf, which causes the /gcc/genhooks.c to 
enter an endless loop when compiling gcc 4.6.0
- it doesnt return the correct value in %n pointer, when something like 
"%*d%n" is used

both bugs are fixed in the following patch. this means a) gcc 4.6.0 
compilation succeeds now, and b) musl now passes the rigorous sscanf 
testsuite of gnu gmp, which is executed when "make check" is called.


here are some testcases
bug 1: EOF (testcase.txt is available here: http://int3.at/testcase.txt )
this one causes GCC compilation to fail

         FILE* f = fopen("testcase.txt", "r");

         while (fscanf (f, "%*[^@]"), buf[0] = '\0',
                  fscanf (f, "@%5[^ \n]", buf) != EOF) {
                 if(*buf) {
                         i++;
                         printf("%d: %s\n",i,buf);
                 }
         }
         fclose(f);

bug 2: %n after %*d
this one causes GMP testsuite to fail

     int i;
         assert(sscanf ("123", "%*d%d", &i) == -1);
         assert(sscanf ("123", "%*d%n", &i) == 0);
         printf("value passed in pointer: %d\n", i); // it seems glibc 
returns 3 in i, while musl returns 2
         ret = sscanf("123" + i, "%d%n", &i);
         printf("%d\n", ret);
         assert(ret == -1);

regards, günter schäffler.






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diff --git a/src/stdio/__scanf.c b/src/stdio/__scanf.c
index 185615d..6e4bd4c 100644
--- a/src/stdio/__scanf.c
+++ b/src/stdio/__scanf.c
@@ -99,8 +99,10 @@ int __scanf(rctx_t *r, const wchar_t *fmt, va_list ap)
 		} else if (*p != '%' || p[1] == '%') {
 			if (*p == '%') p++;
 			r->w = 1;
-			if (*p++ != read(r))
+			if (*p++ != read(r)) {
+				if(r->c == -1) matches = -1;
 				goto match_fail;
+			}
 			continue;
 		}
 		p++;
@@ -126,7 +128,7 @@ int __scanf(rctx_t *r, const wchar_t *fmt, va_list ap)
 		} else if (mode == 1) {
 			dest = va_arg(ap, void *);
 		}
-		
+
 		if (!*p) goto fmt_fail;
 
 		width = 0;
@@ -474,6 +476,7 @@ writefloat:
 		/* unread will do nothing if field width was exhausted */
 		unread(r);
 		if (dest) matches++;
+		else(r->u = 0); //prevent bad size returned with follow-up %n
 	}
 	return matches;
 enc_fail:

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